Internal combustion engines are used as power sources in virtually every conceivable environment. Motorcycles, passenger cars, airplanes, locomotives and ships may all utilize internal combustion engines for propulsion and/or powering of various onboard devices. Generators and power stations may also use a variety of internal combustion engines for production of electrical power. Internal combustion engines can range in size from small engines designed for powered hand tools, to engines approaching the size of a single family home. Over the last century, internal combustion engines have been widely used in relatively large freighters and barges, replacing coal-fired steamers of the 1800's. These and similar internal combustion engines tend to be quite large to provide sufficient power for driving, turning and slowing the massive ships.
Once a relatively large internal combustion engine is started, it is generally undesirable to shut it down unless absolutely necessary, for example for servicing or to avoid a catastrophic engine failure. In marine applications, the reasons for this are at least twofold. First, it can be quite labor intensive to actually start a massive internal combustion engine. Second, enormous vessels can have enormous momentum, and may need powerful reverse or lateral thrust to slow down or turn in a reasonable time, such as when entering port. The ability to reverse propellers, or activate lateral propulsion can also be critical to avoiding collisions.
While maintaining continuous engine operation can be critical, problems with engine operation can seldom be ignored. For example, where a malfunction in one or more of the engine cylinders is detected, attempts to continually operate the engine can result in damage to the affected cylinder(s) and associated components or, worse, catastrophic engine failure. In the latter case, further operation of the engine will be obviously impossible, and no benefit inheres from foregoing shutdown.
Although engineers and operators typically undertake extensive engine diagnostic and maintenance routines, large internal combustion engines can take a significant beating. For example, large marine engines often operate continuously for many hours between maintenance and shutdown. Compounding the operating demands of such engines is the common use of relatively heavy, viscous fuels.
The fuel quantities required to drive a supertanker thousands of miles, for example, are understandably enormous. In an effort to reduce operating costs, many vessel operators find it advantageous to be able to run their engines on not only distillate diesel fuel, but also other relatively inexpensive, residual petroleum fuels. Thus, many marine engines have the capability to switch between a relatively refined fuel such as diesel, and less or non-refined, heavier fuels, often referred to in the industry as residual petroleum fuel. The engine might burn primarily diesel in higher traffic areas or while in port, for example, and might burn the residual fuel primarily while travelling on the high seas. The relative costs of the two fuel types, and local regulations may also affect the decision as to which fuel type to use.
Given the desired flexibility to burn multiple fuel types, the aforementioned marine engines are generally equipped with at least two separate fuel tanks, and various valves and plumbing to apportion the fuel flow from the two tanks as desired. Such systems also often use a common rail or similar fuel delivery system. A typical common rail design includes a pressurized rail or supply line, with a plurality of fuel injectors fluidly connected thereto. Each of the injectors is generally actuated to deliver a measured spray of fuel to an associated cylinder of the engine via one or more fuel injection control valves.
Such systems are also often equipped with various means for limiting overspray or excess fuel flow to the engine cylinders, which can disrupt engine operation and potentially cause engine damage. One such mechanism is known in the art as a mechanical flow limiter. Mechanical flow limiters generally include one or more hydraulically movable components operable to limit or block a fuel flow to one or more engine cylinders, generally following an injection event.
The relatively small, hydraulically sensitive components of a mechanical flow limiter are generally sized and/or designed based at least in part on an approximate viscosity of the fuel flowing therethrough. Accordingly, a mechanical flow limiter design well suited to a relatively lighter, less viscous petroleum distillate such as diesel may not function as well, or at all when used in a system burning a relatively more viscous residual fuel. Residual fuels tend in fact to be so viscous that they must be heated prior to reaching a flowability suitable for delivery via a pressurized supply line and injection through a fuel injector.
The present disclosure is directed to one or more of the problems or shortcomings set forth above.